The center of gravity (CG) of a golf club head is a critical parameter of the club's performance. Upon impact, the position of the CG greatly affects launch angle and flight trajectory of a struck golf ball. Thus, much effort has been made over positioning the center of gravity of golf club heads. To that end, current driver and fairway wood golf club heads are typically formed of lightweight, yet durable material, such as steel or titanium alloys. These materials are typically used to form thin club head walls. Thinner walls are lighter, and thus result in greater discretionary weight, i.e., the portion of the overall weight available for redistribution around a golf club head. Greater discretionary weight allows golf club manufacturers more leeway in assigning club mass to achieve desired golf club head mass distributions.
Various approaches have been implemented for positioning discretionary mass about a golf club head. Many club heads have integral sole weight pads cast into the head at predetermined locations to lower the club head's center of gravity. Also, epoxy may be added to the interior of the club head through the club head's hosel opening to obtain a final desired weight of the club head. To achieve significant localized mass, weights formed of high-density materials have been attached to the sole, skirt, and other parts of a club head. With these weights, the method of installation is critical because the club head endures significant loads at impact with a golf ball, which can dislodge a weight. Thus, such weights are usually permanently attached to the club head and are limited in total mass. This, of course, permanently fixes the club head's center of gravity.
Golf swings vary among golfers, but the total weight and center of gravity location for a given club head is typically set for a standard, or ideal, swing type. Thus, even though the weight may be too light or too heavy, or the center of gravity too far forward or too far rearward, the golfer cannot adjust or customize the club weighting to his or her particular swing. Rather, golfers often must test a number of different types and/or brands of golf clubs to find one that is suited for them. This approach may not provide a golf club with an optimum weight and center of gravity and certainly would eliminate the possibility of altering the performance of a single golf club from one configuration to another and then back again.
One approach to providing “movable weight” is seen in the TaylorMade r7 golf club product lines. In these golf clubs, weights having adjustable masses can be fitted to a fixed number of predetermined locations on the golf club head. This approach allows many fitting situations to be addressed, but there are still some circumstances in which golfers would appreciate greater flexibility.